Refractive index of molten sulphur

Abstract

Detailed measurements have been made, for the first time, of the refractive index, n, of molten sulphur at temperatures up to 200°C. The melt is highly dispersive; at 120°C n varies between 1·94 and 1·86 over the wavelength range 0·6 to 1·8 μm, The data have been analysed to obtain information on the electronic structure of molten sulphur. The effect of melting is small. Below 159°C, S₈ rings are the stable species; above that temperature they polymerize into long chains. The reported measurements suggest that the chains are about 6% more polarizable than the rings, and have an average valence-to-conduction-band gap that is about 1 eV less. Measurements of the absorption coefficient show no anomaly associated with the ring-to-chain polymerization.